LONGER TRAILERS

[cav551]

Carryfast:
Some might call it ignorance.It’s clear that in no case is any length added between the pin and first trailer axle.( Which is fixed ).It’s just a compromised load deck space at the expense of tail sweep design.

donbur.co.uk/gb-en/products/lst … ailers.php

Look at the picture and the axle spacing, Johneboy has said that both rear axles of the bogie steer, I reckon he would have noticed somehow, so I think you need to have another look at your own link and compare the two drawings which show axle spacing and the effective wheelbase. It remains at 8.1 metres but the location of the foremost axle of the bogie alters.

[carryfast]

cav551:

Carryfast:
Some might call it ignorance.It’s clear that in no case is any length added between the pin and first trailer axle.( Which is fixed ).It’s just a compromised load deck space at the expense of tail sweep design.

donbur.co.uk/gb-en/products/lst … ailers.php

Look at the picture and the axle spacing, Johneboy has said that both rear axles of the bogie steer, I reckon he would have noticed somehow, so I think you need to have another look at your own link and compare the two drawings which show axle spacing and the effective wheelbase. It remains at 8.1 metres but the location of the foremost axle of the bogie alters.

It’s the ‘wheelbase’ measurement which I’m referring to.That’s what determines the cut in.

There is no extra load deck length added to the wheelbase which is my point.It’s all added to the tail sweep/swing.In this case they’ve just moved the first axle of a standard type to behind what would be its centre axle which now becomes its first axle.

While a fixed 3 axle type pivots around its centre axle creating ‘fight’ between the cut in affecting the first axle v the tail sweep/swing affecting the third axle.

In this case it pivots around its fixed first axle and anything behind that first fixed axle is tail sweep/swing.Effectively all they’ve done is to maintain the same wheelbase as a standard three axle trailer and stuck a load of extra length on the back of it just as I said.

The ‘steered’ axle/s are only there to go with that extra sweep/swing as opposed to fighting against it.

Obviously any load placed on the deck behind the first axle takes weight off the pin and drops it on the second and third axles.Combined with the remaining gross weight limit.

Meaning that the extra length is a waste of space in terms of tonne/miles/per gallon.In addition to obviously being a liability to its driver in a sharp turn.Owing to its out of sight out of mind catastrophic amounts of tail sweep/swing.

[johneboy]

Carryfast:

robthedog:
CF you are so out of touch the rear does steer and push to the other side reducing cut in so much so it will hit obstacles on the other side, and weight distribution is the same as any artic don’t get involved in stuff you know nothing about

As I said unless ‘all’ three steer then axles 2 and/or 3 ‘steering’ can’t possibly ‘push’ the fixed axle 1 anywhere. You’re obviously confusing tail sweep/swing with a proper STGO rear steer set up.Unless it’s STGO then standard pin to axle and resulting cut in rules apply.All you’ve got is increased tail sweep and an obviously longer load deck length behind trailer axles one and two which also means a totally different weight distribution regime.

Right ,one last go, and I’ll try to explain it as simple as I can.

Imagine pulling a trailer with fixed axles. When turning, the first and third axles will fight against each other trying to turn in the opposite (sideways) directions . Now, the tighter you turn, the tyres on both axles scrub sideways over the road surface to the point that at extreme angles and loaded it looks like the tyre is about to be pulled off the rim. This means that the first axle scrubbing sideways contributes to trailer cut in. Are we in agreement so far?
Now, put rear steer(s) into the equation and all of a sudden the first axle has nothing to fight against because the rear axle(s) steer away from the fight, therefore the sideways scrub is all but eliminated and the usual amount of first axle cut in is reduced.
This means standard pin to axle cut in rules do NOT apply … and it’s not STGO.
So if standard rules don’t apply it gives scope to tinker with axle positions.

And that’s enough banging my head against the wall with this thread. I’m oot

[don-bur]

We thought we’d add a bit of clarity regarding both the regulation and engineering to meet the LST requirements.

Firstly, in order for a normal length trailer to be “deemed to comply” with the inner 5.3m turning circle regulations, the wheelbase (kingpin to centre of bogie) cannot exceed 8.135m. This is calculated using geometry if the cab front is skirting inside a 12.5m outer turning circle. In reality, a standard trailer will cut into the 5.3m circle slightly due to scrub effects.

Typically, we manufacture with a wheelbase of 8.1m (1.310 axle spacing). Some are slightly shorter at 7.8m or 7.9m for extra manoeuvrability.

When Longer Semi Trailers were introduced, the “Deemed to comply” regulation was overturned in favour of physical compliance. This meant that the wheelbase had to be slightly shorter so the wheels did not cut into the 5.3m inner turning circle.

This becomes a little complicated because, uniquely, an LST has 2 bogies: a fixed front bogie (typically a standard tandem setup but can be a single axle with the centre set at approx 7.9m wheelbase) + another bogie (single steer or tandem steer axle) set further back to cope with the rearward shift in weight so as not to overload the axles.

This means that, to prevent massive scrub on the fixed bogie tyres, the rear bogie(s) has to be steered. The most common, cost-effective, type is self steer but these are tricky when reversing as they don’t easily self-lock in tight yards. The other solution is positive steer (Not command steer found on STGO low-loaders).

In terms of weight distribution, we can confirm the following for a fully freighted trailer:

Standard 13.7m (8.1m wheelbase with 13m long load @ 28T): Kingpin Weight: 12,563kgs / Bogie weight: 22,936kgs
LST 15.650m (7.925m wheelbase to centre of tandem fixed bogie + 2.07m to rear self-steer axle with 15m long load @ 25.9T): Kingpin Weight: 10,464kgs / Bogie Weight: 23,995kgs EDITED
LST 15.650m (7.450m wheelbase to front fixed axle + 2 rear positive steer axles with 15m long load @ 27T): Kingpin Weight: 11,876kgs / Bogie Weight: 23,623kgs

It’s difficult to compare eggs with eggs here as the max payload weight differs with each solution.

We know that the low accident report rate coming from Risk Solutions Ltd on behalf of the DfT reflects carefully selected drivers who have had more training; particularly regarding swing-out at the rear. It is plausible that the RIDDOR accident rate might increase in line with 13.6/13.7m long trailers if LSTs became approved and released for general use.

We also know that, under the terms of the “Operator Undertaking” reports that go back to Risk solutions, every % fill and % weight capacity is recorded so productivity is measured relative to an operators “normal” load, whether that be heavy, dense loads or light, high volume loads.

We hope this helps.

[carryfast]

Don-Bur:
We thought we’d add a bit of clarity regarding both the regulation and engineering to meet the LST requirements.

Firstly, in order for a normal length trailer to be “deemed to comply” with the inner 5.3m turning circle regulations, the wheelbase (kingpin to centre of bogie) cannot exceed 8.135m. This is calculated using geometry if the cab front is skirting inside a 12.5m outer turning circle. In reality, a standard trailer will cut into the 5.3m circle slightly due to scrub effects.

Typically, we manufacture with a wheelbase of 8.1m. Some are slightly shorter at 7.8m or 7.9m for extra manoeuvrability.

When Longer Semi Trailers were introduced, the “Deemed to comply” regulation was overturned in favour of physical compliance. This meant that the wheelbase had to be slightly shorter so the wheels did not cut into the 5.3m inner turning circle.

This becomes a little complicated because, uniquely, an LST has 2 bogies: a fixed front bogie (typically a standard tandem setup but can be a single axle with the centre set at approx 7.9m wheelbase) + another bogie (single steer or tandem steer axle) set further back to cope with the rearward shift in weight so as not to overload the axles.

This means that, to prevent massive scrub on the fixed bogie tyres, the rear bogie(s) has to be steered. The most common, cost-effective, type is self steer but these are tricky when reversing as they don’t easily self-lock in tight yards. The other solution is positive steer (Not command steer found on STGO low-loaders).

In terms of weight distribution, we can confirm the following for a fully freighted trailer:

Standard 13.7m curtainsider (8.1m wheelbase with 13m long load): Kingpin Weight: 12,563kgs / Bogie weight: 22,936kgs
LST trailer 15.650m curtainsider (7.925m wheelbase to centre of fixed bogie + 2m to rear axle with 15m long load): Kingpin Weight: 13,977kgs / Bogie Weight: 21,522kgs

In summary, due to the longer load ( for same weight ) and elongation of bogie shifts weight bias more onto the pin : despite having a longer rear overhang.

We know that the low accident report rate coming from Risk Solutions Ltd on behalf of the DfT reflects carefully selected drivers who have had more training; particularly regarding swing-out at the rear. It is plausible that the RIDDOR accident rate might increase in line with 13.6/13.7m long trailers if LSTs became approved and released for general use.

We also know that, under the terms of the “Operator Undertaking” reports that go back to Risk solutions, every % fill and % weight capacity is recorded so productivity is measured relative to an operators “normal” load, whether that be heavy, dense loads or light, high volume loads.

We hope this helps.

So firstly it would be fair to say that the regs have created a situation in which drivers are lumbered with considerably more tail sweep than standard knowing that corner is out of sight from the moment the vehicle starts to turn.Also for no return in tonne/mile/per gallon efficiency for the operator or road space etc.

Which leaves the question how does more rear overhang translate as more weight on the pin.The only possible explanation is that pallet weights have to be reduced regarding any of the load behind the first trailer axle and correspondingly increased ahead of it.Obviously to maintain gross weight limits and the laws of physics that anything behind trailer axle 1 imposes weight on trailer axles 2 and 3 while lifting weight off the pin ?.While anything behind trailer axle 2 imposes weight on axle 3 while lifting some more of the pin and some off trailer axle 1 and anything behind axle 3 imposes even more load on axle 3 while lifting it off the pin and trailer axles 1 and 2 ?.

IE you can’t change the laws of physics regarding force times distance and the relative pivot points of a ‘see saw’ ( trailer axles ) with the enforced positioning of trailer axle 1 being the elephant in the room in that regard being the first pivot point of the see saw which governs the rest ?.

In all cases this design being a lose lose compromise enforced by cut in regulations and gross weight restrictions.
As opposed to a proper Scandinavian type LHV design which would maintain reasonable cut in without increasing tail sweep.All using standard existing vehicle and trailer types.
With the bonus of even more load deck length and increased tonne/mile/per gallon efficiency ‘if’ the politically driven rail protectionist shackles were removed.

[franglais]

Carryfast:

Don-Bur:
We thought we’d add a bit of clarity regarding both the regulation and engineering to meet the LST requirements.

Firstly, in order for a normal length trailer to be “deemed to comply” with the inner 5.3m turning circle regulations, the wheelbase (kingpin to centre of bogie) cannot exceed 8.135m. This is calculated using geometry if the cab front is skirting inside a 12.5m outer turning circle. In reality, a standard trailer will cut into the 5.3m circle slightly due to scrub effects.

Typically, we manufacture with a wheelbase of 8.1m. Some are slightly shorter at 7.8m or 7.9m for extra manoeuvrability.

When Longer Semi Trailers were introduced, the “Deemed to comply” regulation was overturned in favour of physical compliance. This meant that the wheelbase had to be slightly shorter so the wheels did not cut into the 5.3m inner turning circle.

This becomes a little complicated because, uniquely, an LST has 2 bogies: a fixed front bogie (typically a standard tandem setup but can be a single axle with the centre set at approx 7.9m wheelbase) + another bogie (single steer or tandem steer axle) set further back to cope with the rearward shift in weight so as not to overload the axles.

This means that, to prevent massive scrub on the fixed bogie tyres, the rear bogie(s) has to be steered. The most common, cost-effective, type is self steer but these are tricky when reversing as they don’t easily self-lock in tight yards. The other solution is positive steer (Not command steer found on STGO low-loaders).

In terms of weight distribution, we can confirm the following for a fully freighted trailer:

Standard 13.7m curtainsider (8.1m wheelbase with 13m long load): Kingpin Weight: 12,563kgs / Bogie weight: 22,936kgs
LST trailer 15.650m curtainsider (7.925m wheelbase to centre of fixed bogie + 2m to rear axle with 15m long load): Kingpin Weight: 13,977kgs / Bogie Weight: 21,522kgs

In summary, due to the longer load ( for same weight ) and elongation of bogie shifts weight bias more onto the pin : despite having a longer rear overhang.

We know that the low accident report rate coming from Risk Solutions Ltd on behalf of the DfT reflects carefully selected drivers who have had more training; particularly regarding swing-out at the rear. It is plausible that the RIDDOR accident rate might increase in line with 13.6/13.7m long trailers if LSTs became approved and released for general use.

We also know that, under the terms of the “Operator Undertaking” reports that go back to Risk solutions, every % fill and % weight capacity is recorded so productivity is measured relative to an operators “normal” load, whether that be heavy, dense loads or light, high volume loads.

We hope this helps.

So firstly it would be fair to say that the regs have created a situation in which drivers are lumbered with considerably more tail sweep than standard knowing that corner is out of sight from the moment the vehicle starts to turn.Also for no return in tonne/mile/per gallon efficiency for the operator or road space etc.

Which leaves the question how does more rear overhang translate as more weight on the pin.The only possible explanation is that pallet weights have to be reduced regarding any of the load behind the first trailer axle and correspondingly increased ahead of it.Obviously to maintain gross weight limits and the laws of physics that anything behind trailer axle 1 imposes weight on trailer axles 2 and 3 while lifting weight off the pin ?.While anything behind trailer axle 2 imposes weight on axle 3 while lifting some more of the pin and some off trailer axle 1 and anything behind axle 3 imposes even more load on axle 3 while lifting it off the pin and trailer axles 1 and 2 ?.

IE you can’t change the laws of physics regarding force times distance and the relative pivot points of a ‘see saw’ ( trailer axles ) with the enforced positioning of trailer axle 1 being the elephant in the room in that regard being the first pivot point of the see saw which governs the rest ?.

In all cases this design being a lose lose compromise enforced by cut in regulations and gross weight restrictions.
As opposed to a proper Scandinavian type LHV design which would maintain reasonable cut in without increasing tail sweep.All using standard existing vehicle and trailer types.
With the bonus of even more load deck length and increased tonne/mile/per gallon efficiency ‘if’ the politically driven rail protectionist shackles were removed.

Dear Don Bur,
Of you consider replying to this, I strongly advise you to read up on the role of the Sudeten Germans in the American “so called Civil War”, and why the atmosphere on Mars is definitive proof that climate change on Planet Earth is a myth perpetuated by those who believe it is round rather than flat.
Once your thought processes are primed you may not feel like entering the fray, however. Good luck.

[carryfast]

Franglais:
Of you consider replying to this, I strongly advise you to read up on the role of the Sudeten Germans in the American “so called Civil War”, and why the atmosphere on Mars is definitive proof that climate change on Planet Earth is a myth perpetuated by those who believe it is round rather than flat.
Once your thought processes are primed you may not feel like entering the fray, however. Good luck.

For the avoidance of any doubt.
No one is saying that the Germans fighting for the Union side who were involved in the St Louis Arsenal massacre had any connection with the Sudetenland.

However the maths which say that dropping a load of 1 tonne pallets behind the first trailer axle of an LST, let alone behind the second or third, will ‘add’ weight at the ‘pin’. Seem similar to that which says that Venus was cooked by the CO2 component of its atmosphere.Not the pressure of that atmosphere combined with the closer distance to the Sun.

While we’ve got an admission that it adds loads to the tail sweep.Which is a bit like saying that 0.04% CO2 isn’t going to cook the planet nor the bit extra added to that if we burn all the oil and coal left in the ground.

[star_down_under]

Johneboy:
As for your productivity argument, if you take it to the extreme would that mean you’re in favour of Australian type road trains delivering bog roll to rdc’s as to get the tons/mile?

That’d be worth watching. Carryfast trying to manoeuvre a 55 metre, four trailer combination, with six articulation points, onto a dock.

[carryfast]

Star down under.:

Johneboy:
As for your productivity argument, if you take it to the extreme would that mean you’re in favour of Australian type road trains delivering bog roll to rdc’s as to get the tons/mile?

That’d be worth watching. Carryfast trying to manoeuvre a 55 metre, four trailer combination, with six articulation points, onto a dock.

Now you’re just being silly.

Anyone knows that four trailers have 7 points of artic.Unless the prime mover is a proper rigid like it should be then its 8 and in either case it’s going nowhere fast backwards just like 3.

I was actually referring to something along the lines of this.60t + gross and more bog roll than the LST and it’s also driveable here.

youtube.com/watch?v=WvBuk3gR_xo

[don-bur]

Carryfast:
… how does more rear overhang translate as more weight on the pin…

After checking with engineering, they had only increased body length. This has now been re-calculated.

For the example calculated, we’ve had to reduce payload to 25,900kgs to prevent overloading the rear bogie.

We are correcting the first post.

Due to the dynamics of air suspension, the load is equalised across the rear bogie(s) so the effective wheelbase is kingpin to centreline of the bogie(s).

Below, I’ve also added the less-common solution with fixed front axle (forming the basis for the wheelbase) and 2 rear positive steer axles.

[star_down_under]

Carryfast:

Star down under.:

Johneboy:
As for your productivity argument, if you take it to the extreme would that mean you’re in favour of Australian type road trains delivering bog roll to rdc’s as to get the tons/mile?

That’d be worth watching. Carryfast trying to manoeuvre a 55 metre, four trailer combination, with six articulation points, onto a dock.

Now you’re just being silly.

Anyone knows that four trailers have 7 points of artic.Unless the prime mover is a proper rigid like it should be then its 8 and in either case it’s going nowhere fast backwards just like 3.

I was actually referring to something along the lines of this.60t + gross and more bog roll than the LST and it’s also driveable here.

youtube.com/watch?v=WvBuk3gR_xo

Anybody? I’ve lost count of the 100k s of kilometres I’ve driven them, how many have you driven? Just as I thought, you’ve only seen pictures.
A general access quad is a BABB combination, I’ve made and broken up plenty of them. Believed me, there are only six articulation points.

[carryfast]

Star down under.:

Carryfast:
Anyone knows that four trailers have 7 points of artic.Unless the prime mover is a proper rigid like it should be then its 8 and in either case it’s going nowhere fast backwards just like 3.

I was actually referring to something along the lines of this.60t + gross and more bog roll than the LST and it’s also driveable here.

youtube.com/watch?v=WvBuk3gR_xo

Anybody? I’ve lost count of the 100k s of kilometres I’ve driven them, how many have you driven? Just as I thought, you’ve only seen pictures.
A general access quad is a BABB combination, I’ve made and broken up plenty of them. Believed me, there are only six articulation points.

So what’s the max GCW/Payload of a BABB v GTW/Payload of an AAAA.

A frame drawbars road trains it’s all a variation of a theme if you’re familiar with one it’s just a case of chucking more trailers on it if there’s road space and given a sensible government.What is certain is anything with much more than 3 points of artic is going nowhere fast backwards.

Which leaves the question of the flawed LST idea v the proper Scandinavian type LHV which every other sensible European country is looking at.

[star_down_under]

Carryfast:

Star down under.:

Carryfast:
Anyone knows that four trailers have 7 points of artic.Unless the prime mover is a proper rigid like it should be then its 8 and in either case it’s going nowhere fast backwards just like 3.

I was actually referring to something along the lines of this.60t + gross and more bog roll than the LST and it’s also driveable here.

youtube.com/watch?v=WvBuk3gR_xo

Anybody? I’ve lost count of the 100k s of kilometres I’ve driven them, how many have you driven? Just as I thought, you’ve only seen pictures.
A general access quad is a BABB combination, I’ve made and broken up plenty of them. Believed me, there are only six articulation points.

So what’s the max GCW/Payload of a BABB v GTW/Payload of an AAAA.

A frame drawbars road trains it’s all a variation of a theme if you’re familiar with one it’s just a case of chucking more trailers on it if there’s road space and given a sensible government.What is certain is anything with much more than 3 points of artic is going nowhere fast backwards.

Which leaves the question of the flawed LST idea v the proper Scandinavian type LHV which every other sensible European country is looking at.

Totally depends on which scheme is being utilised and can vary from state to state.
Generally speaking, rule of thumb:
Single axle steer: 6 tonne.
Bogie axle: 16.5 - 17 tonne.
Tri axle: 20 - 22.5 tonne
GCM: 11.9 - 130 tonne.
Individual variations can be endorsed under PBS.
Universally in general haulage, tri axle trailer are utilised with tri axle, converter dollies becoming the norm.

Triple roadtrains, with 5 articulation points are reversed as a matter of course.